First things first! Preheat your oven to 350°F (175°C). This ensures that your bake will cook evenly and thoroughly. While it heats up, you can prep the other ingredients.

Heat 2 tablespoons of extra-virgin olive oil in a skillet over medium heat. Once hot, toss in the thinly sliced onion. Sauté them for about 5–7 minutes until they become translucent and slightly caramelized. This adds a lovely sweetness to your bake. Stir occasionally so they don’t stick.

In a large mixing bowl, crack all 12 eggs. Pour in ½ cup of whole milk, 1 tablespoon Dijon mustard, 1 teaspoon fine sea salt, and freshly ground black pepper to taste. Whisk these ingredients together until well combined. You want a fluffy mixture!

Once the eggs are whisked, it’s time to add some heartiness. Stir in the diced smoked ham and baby spinach. The spinach will wilt while baking, blending beautifully with the ham. If you’re using thyme or smoked paprika, toss that in now too.

Take your croissants and tear them into bite-sized pieces. The more rustic, the better! Add these pieces to a greased 9x13 inch baking dish. Pour the egg, ham, and spinach mixture over the croissants. Give it a gentle mix with a spatula to ensure the croissants soak up that delicious egg mixture.

Finally, sprinkle 1 cup of shredded cheese over the top. Opt for a generous layer! The cheese will melt and create a bubbling, golden crust that everyone will rave about.

Pop your dish into the preheated oven. Bake for 30–35 minutes, or until the eggs are set and the top is golden brown. If you shake the dish slightly and the center jiggles, give it a few more minutes. Every oven is a bit different.

Once out of the oven, let it cool for about 5–10 minutes. This allows everything to settle, making it easier to cut into squares. Serve warm, and watch your friends and family swoon.